This invention relates to methods of dyeing polymers, more specifically, methods of enhancing the dyeability of polymers.
Dyeing polymers such as polyolefins (e.g., polypropylene) has been a challenge to polymer and textile chemists for many decades. Currently available approaches rely mainly on copolymerization, polyblending, grafting, and plasma treatment technologies. Examples of such polymers include vinylpyridine/styrene copolymers; poly(ethylene/vinyl acetate) blended with polypropylene for disperse dyeability; stearyl methacrylate, dimethylaminopropylacrylamide, or basic imidized styrene-maleic anhydride copolymer for acid and disperse dyeability; stearyl methacrylate-maleic anhydride for basic and disperse dyeability; and organo-metal-complexes for specially selected dyes. See, e.g., Akrman et al, Journal of the Society of Dyers and Colourists, 114, 209-215 (1998); Luc et al., International Dyer, 32-36 (1998); and U.S. Pat. Nos. 6,127,480, 6,039,767, 5,985,999, 5,576,366, 5,550,192, and 5,468,259.
One disadvantage of these technologies is that the y considerably in crease the costs of the dyed products due to the cost increase of the process and materials. Another disadvantage is that some of these technologies are not suitable for producing fine fibers used in clothing materials.
The invention is based on the discovery that the dyeability of polymers, such as polyolefins, can be significantly enhanced by incorporating into the polymers a nanomaterial such as a nanoclay, nanosilica, metal oxide (e.g., zinc oxide, silver oxide, calcium oxide, platinum oxide), zeolite, or nanoparticles of polymers (e.g., polysiloxanes). The term xe2x80x9cdyeabilityxe2x80x9d refers to a polymer""s ability to be dyed, the r ate at which the polymer can be dyed, the amount of dye that can be applied to the polymer (i.e., dye exhaustion), and the fastness of the dyes on the dyed polymers.
Accordingly, the invention is related to methods of dyeing polymers by first dispersing a nanomaterial into the polymer to form a polymer nanocomposite, and then dyeing the polymer nanocomposite with a dye.
A xe2x80x9cnanomaterialxe2x80x9d refers to a particulate inorganic or organic compound or composition having a particle size in the range of 1-1,000 nm (e.g., 50-200 nm or 200-600 nm). Nanomaterials thus include nanoclay, nanosilica, metal oxides (e.g., zinc oxide, silver oxide, calcium oxide, or titanium oxide), zeolites, and nanoparticles of a polymer. Nanomaterials can be pretreated with ionic surfactants (e.g., alkyl ammonium salts or fluoro-organic compounds) for enhanced compatibility with the polymer (e.g., enhanced hydrophilicity, hydrophobicity, or amphiphilicity, depending on the hydrophilicity or hydrophobicity of the polymers), and subsequent improved (i.e., more even) dispersion, depending on the polymers.
The new methods are applicable to all polymers that need to be dyed including those polymers that may be difficult to dye using known techniques. Such polymers include polyvinyls (e.g., polystyrene), epoxy resins, polyolefins (e.g., polypropylene), polyamides (e.g., nylon 6), aromatic polyamide (e.g., aramid), polyimides (e.g., polypyromellitimide), polyanhydrides (e.g., polymaleic anhydride), acrylic polymers (e.g., polymethyl methacrylate), polyesters (e.g., poly(ethylene terephthalate)), polyimines (e.g., polyethyleneimine), polysaccharides (e.g. rayon), polypeptides (e.g., zein), polylactones (e.g., polycaprolatone), and their random or block copolymers. Useful polymers also include derivatives of polymers, e.g., polymers with ester derivatives on side acidic groups. The molecular weights of the polymers can be in the range of 15,000 to 150,000, and they can be amorphous or highly crystalline.
The methods are particularly suitable for polymers which are difficult to dye. Such polymers, which generally have no or very limited dyeability, include polyolefins, polyvinyls, aromatic polyamides, and epoxy resins.
Embodiments of the new methods include those in which the polymers are polyvinyls, epoxy resins, polyolefins, polyamides, aromatic polyamides, polyimides, polyanhydrides, acrylic polymers, polyesters, polyimines, polysaccharides, polypeptides, polylactones, or a random or block copolymers thereof; and those in which the weight ratio of the nanomaterial to the polymer is in the range of 0.01-20% (e.g., 0.1-10% or 0.5-5%).
The polymer nanocomposites thus obtained can be in the form of fibers, films, membranes, tubes, or particles.
The invention also relates to novel dyed polymer nanocomposites, each containing dye molecules, a polymer, and a nanomaterial dispersed in the polymer. The dyed polymer nanocomposites can be prepared by first obtaining polymer nanocomposites and then dyeing the polymer nanocomposites.
Also within the scope of the invention are articles made of the novel dyed polymer nanocomposites.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
The new methods and dyed polymers provide numerous advantages. For example, the methods are relatively inexpensive and easy to carry out. In addition, the dyed polymers can be easily processed and have excellent mechanical strength, tensile strength, gas impermeability, flame retardance, and heat resistance. The dyeability of the resultant nanocomposites (e.g., dye exhaustion rate and colorfastness) can be engineered based on the selection of the nanomaterials and the modification of the process.